Made in Arabic
alidade
العِضادة
On the back of the astrolabe a rule turns about its centre; sighted through its two holes at the sun or a star, it gives the altitude on the rim. Arabic called it al-ʿiḍāda, Latin took it over as alhidada, and English has it as alidade – still the name of the sighting rule on surveyors' instruments.
- Instrument
- the astrolabe, its back
- Written on it in Arabic
- On the same back, on the two shadow squares: «ẓill aqdām mustawī» and «ẓill aqdām maʿkūs», which Latin rendered umbra recta and umbra versa; and the maker's signature, «made by Muhammad Muqim al-Yazdi».
The path between languagesal-ʿiḍāda → alhidada → alidade
أ.د. عبد العزيز الحميد، متحف جامعة الإمام
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Sources
- Oxford English Dictionary / Merriam-Webster: alidade, from Medieval Latin alhidada, from Arabic al-ʿiḍāda
- Museum of the History of Science, Oxford: astrolabe of Muhammad Muqim al-Yazdi for Shah Abbas II (1647), the original of this model
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